Aroma-active compounds in brown butter

Brown butter has gained popularity as an ingredient, yet its flavor chemistry remains uncharacterized. This study characterized the aroma-active compounds and sensory properties of brown butter. Duplicate lots of salted and unsalted fresh butter were obtained from a manufacturer, and a standardized browning method was developed. Brown and unheated butters were evaluated by descriptive analysis and instrumental color analysis. Volatiles were extracted using headspace solid-phase microextraction and direct solvent extraction followed by solvent-assisted flavor evaporation and analyzed by gas chromatography-mass spectrometry, gas chromatography-olfactometry, and gas chromatography-tandem mass spectrometry. Aroma extract dilution analysis, stable isotope dilution analysis, sensory threshold determination, odor activity values, and model systems were used to identify, quantify and determine key aroma contributors. Brown butter exhibited higher intensities of cooked-nutty, caramel, and brown-toasted flavors compared with unheated butters. Brown butter was characterized by browned color, Maillard reaction derived volatiles, lipid oxidation products, and select sulfur compounds, while other low molecular weight volatiles decreased. Furaneol, diacetyl, and 2-nonanone as well as other aldehydes, ketones, lactones and sulfur compounds were identified as key contributors to brown butter aroma. These findings provide a comprehensive chemical and sensory framework for understanding brown butter flavor development and highlight the importance of thermal processing conditions in shaping butter aroma and flavor through Maillard reaction and lipid degradation pathways.